"I am thrilled with how this came out," West says, on Mountain's official site. "Other guests are on as well, but that will come in a little while. I am excited for the sound on this; it's extraordinary, if I do say so myself."

Soundcheck, which doesn't have an officially announced release date just yet, is West's first solo project since 2013's Still Climbing. That followed a harrowing period of diabetes-related health issues for West, who had his lower right leg amputated in 2011. Unusual Suspects, a solo album from the same year, also had an all-star cast – including Billy Gibbons, Slash, Steve Lukather and others.

Mountain was originally co-founded by West and Felix Pappalardi, then working as Cream's producer, and named after the title of West's debut solo project. The group appeared on Day 2 of 1969's Woodstock festival. Corky Laing joined not long after, and Mountain took the heavy-rocking "Mississippi Queen" to No. 21 on the Billboard charts.

Pappalardi split with Mountain in 1974, only to die tragically, leaving West and Laing to work on various side projects before reforming Mountain in the early '80s. West collaborated with the Who on sessions for 1971's Who's Next; he's also recorded with Ian Gillan, Ozzy Osbourne and Johnny Winter.